General John Abizaid, who is responsible for military operations in Iraq, told the Senate Armed Services Committee on Wednesday: "From evidence already gathered, we believe that systemic problems existed at the prison and may have contributed to events there."
Abizaid told the committee he took personal responsibility but said the abuse would not deflect US forces from their task in Iraq.
He added: "We will follow the trail of evidence wherever it leads. We will continue to correct systemic problems. We will hold people accountable and, in accordance with the Uniform Code of Military Justice, we will take appropriate action."
Also testifying were Army Lieutenant General Ricardo Sanchez, commander of ground forces in Iraq, and Major General Geoffrey Miller, deputy commander for detainee operations in Iraq.
Red Cross warnings
Committee Chairman John Warner, a Virginia Republican, said it was time for US top military leaders to face American and world public opinion.
The Abu Ghraib pictures have
US Senator Carl Levin, a Michigan Democrat, said he wanted to know about warnings from the International Committee of the Red Cross that Iraqi prisoners were being abused that surfaced as early as May 2003, months before the US military launched its first investigation.
The hearing happenned on the same day as a US special court-martial sentenced Specialist Jeremy Sivits to one year in prison and ordered him discharged from the army for bad conduct over the abuse of Iraqi prisoners at Abu Ghraib.
Sivits, 24, pleaded guilty and promised to testify against some of the six other soldiers indicted. He also confessed to pushing a prisoner into the now infamous picture of a pile of naked Iraqis.
Warner has said he wants to talk with other officials, including the US administrator in Iraq, Paul Bremer, and Under Secretary of Defense Douglas Feith and wants to see documents and legal reviews of "harsh approaches" on detainee interrogations.
However, the Pentagon is disputing a report that the abuse of Iraqi prisoners grew out of a secret plan approved by Defence Secretary Donald Rumsfeld to toughen interrogation methods to fight a growing insurgency.
"I think this issue needs to be resolved because it directly impacts American support for our effort in winning this war, and that support is clearly eroded since this thing broke," Senator John McCain, an Arizona Republican, said of the scandal of Iraqi detainees being abused and sexually humiliated.
"From evidence already gathered, we believe that systemic problems existed at the prison and may have contributed to events there"
General John Abizaid,
Commander of military operations in Iraq
But House of Representatives Armed Services Committee Chairman Duncan Hunter, a California Republican, said he disagreed with Warner's plans to hold more hearings.
"The Senate will do lots of great stand-up shots and they will go out and do stakeouts with the press and they will be able to adorn the talk shows for the next four, five days," Hunter said.
"I would hope that we can refocus now that we have spent this enormous amount of publicity on this prison thing. We have to refocus on this war."